The present invention relates to a belt including a detection target portion, a transfer belt unit and an image forming apparatus using the belt.
In electrophotographic image forming apparatuses, a plurality of belt-like transfer members such as an intermediate transfer belt and a transfer belt are used.
For example, in a color image forming apparatus, a position of the belt-like transfer member is controlled with high accuracy in order to prevent displacement of toner images of respective colors (for example, yellow, magenta, cyan, black or the like). Further, in a printer using a continuous recording medium such as a rolled paper, the position of the belt-like transfer member is controlled with high accuracy in order to prevent displacement of a writing starting position due to extension or speed variation of the belt-like transfer member.
In order to control the position of the belt-like transfer member with high accuracy, there is proposed an image forming apparatus including a belt-like transfer member on which a position detection mark is formed. A position and speed of the belt-like transfer member is controlled by detecting the position detection mark formed on the belt-like transfer member using a position detection unit. The position detection mark is formed of an adhesive tape bonded to the belt-like transfer member. The adhesive tape reflects or absorbs light (see, for example, Japanese Application Publication No. H6-56292).
However, there are cases where the position detection mark separates from the belt-like transfer member when an adhesive force decreases.